In a known device, the base plate on which the brush-holders are disposed is provided with holding means for attachment of the current bus. The base plate and thereby the brush-holding device, however, is fastened to a part other than the field winding which is connected to the current bus. In this known device, therefore, there is the disadvantage that manufacturing tolerances for the brush-holder device and for the parts carrying the field winding cannot be balanced out. This results in stresses at the place of connection between the current bus and the field winding. If the field winding is soldered to the current bus, the solder joint can break. If the field winding is detachably connected to the current bus, supplementary means for compensating for the axial and radial deviations of the place of connection to the field winding and current bus are necessary.